The objectives of this project are to elucidate the anatomical substrates of long-latency event-related potentials (ERPs) and associated cognitive functions, in particular those related to selective attention, and to clarify the relationships between cognitve deficits and ERP abnromalities. The N; and P2 components of the auditory potential, the attention-related negativety elicited during a dichotic listening task and the P300 wave associated with auditory and visual target detection will be studied. The proposed experiments involve the recording of these types of ERPs in conjuction with psychological testing in patients with circumscribed structural brain lesions as revealed by CT scan. Assessment of the effects of focal brain lesions in different locations will provide information about the neural substrates of the ERPs and their associated psychological processes. A comprehensive neuropsychological battery of tests will be adminstered to each subject, including the WAIS, aphasia screening test, Boston Naming Test, parietal lobe battery, Wiscosin card sorting, tests of verbal and non-verbal memory and a selective attention assessment. An understanding of the electrophysiological correlates of attentional and memory deficits associated with particular brain lesions will be not only of theoretical interest, but will also help to evaluate attentional and cognitve deficits in patients with specific brain lesions.